A number of medical conditions may be treated in a minimally invasive manner with various kinds of catheters designed to reach treatment sites internal to a patient's body. Balloon catheters, for example, may be employed in angioplasty procedures to widen obstructed blood vessels and optionally deliver stents, or in procedures to treat atrial fibrillation, atrial flutter and ventricular tachycardia by forming therapeutic lesions in the soft tissue in the heart. In some procedures, expansion of the balloon at the treatment site may provide the desired therapy, such as expanding an obstructed blood vessel during an angioplasty procedure. In other procedures, an energy source within the balloon can deliver the desired therapy and, in these procedures, the balloon can serve to either position the energy source or communicate energy to or from the soft tissue to form the desired therapeutic lesions. For example, in procedures for treating atrial fibrillation, a balloon catheter can be used to position a radio frequency energy source in proximity to the tissue to be treated and, similarly, in cryoablation procedures for treating atrial fibrillation, a balloon catheter can be used to deliver cryotherapy or extract heat, through the surface of the balloon, from the soft tissue.